There are some mobile phones, PDA, and other portable communication apparatus with storage functions capable of storing the personal private information such as address book and schedule. In order to prevent another person from using the communication apparatus and further, grabbing the private information stored in the communication apparatus, the communication apparatus usually needs more securing function to secure the private information against grabbing.
Taking the present mobile phone as an example, the user generally needs to insert the Subscriber Identity Module (SIM) card to start the communicating function of the mobile phone. The SIM card usually has the function of generating a cipher key. The calculating algorithm in the SIM card for generating the cipher key can be Hash-based Message Authentication Code (HMAC), GSM-A3, GSM-A8. It is very difficult to crack the calculating algorithm. Consequently, the SIM card is the most popular securing system. There are two method of securing the private information associated with the subscriber. One is to lock the SIM card by a password that is inputted by the users, and the other is to lock the mobile phone by a password.
The first method according to the prior art takes advantage of the SIM card to secure private information associated with the subscriber. However, the first method according to the prior art only secures private information that stored in the SIM card, without securing the information stored in the mobile phone. As a result, when a user loses his mobile phone, the other person can use this mobile phone by another SIM card, even grab the information stored in the phone.
The second method according to the prior art takes advantage of the password to lock the mobile phone. When a user loses his mobile phone, the other person needs to input the password to unlock this mobile phone even though the other person has a SIM card. By this way, it can resolve the drawback of the first method according to the prior art. Nevertheless, if many persons want to use the same mobile phone, it needs another system to verify the different IDs and their corresponding passwords. This results in the more complicated system and high cost.
Besides, the safety of the second method according to the prior art depends on the circuit design of mobile phone. Generally speaking, the circuit design of mobile phone is not good enough to take severe precautions against the cracker.